Exotic Pest Plants

Chinese tallow tree, Triadica sebifera

The term, “exotic pest plant,” has a specific definition. An exotic plant is one that is not native. It could be an Australian plant grown in the United States or plant that is cultivated in another part of the same state where it does not occur naturally. An exotic pest plant is a non-native plant that has escaped into natural areas and is changing the natural environment. Typically, this does not include the garden and roadside weeds that thrive only in disturbed environments.

The exotic pest plant issue tends to be an emotional one. Ecologists around the world are working to control exotic pest plants in natural areas. It is a difficult task and, at times, feels overwhelming. They do not understand why gardeners are not satisfied with native plants, why gardeners need ever more exotic plants or why they do not seem to care about this issue. Some biologists have tried to stop the introduction of all new exotic plants to the United States.

At the other end of the spectrum are avid gardeners who are always looking for an exciting new plant. They are willing to go to great cost to obtain these plants and great lengths to insure the success of these plants in their gardens. In their zeal, a few of them have contributed to the problem by distributing seeds into natural areas to “beautify” these wild spaces.

The vast majority of us reside somewhere in the middle between these extremes, usually without giving the matter much thought. We appreciate nature and we enjoy an attractive garden. Some of us plant exotic pest plants in our gardens or allow them to grow in our landscapes without being aware of the problems that they cause.

The vast majority of the thousands of plant species we grow in our gardens are not invasive. Most grow with a little care but do not spread aggressively. Some are a challenge to keep alive. A huge nursery industry is based on these plants. More importantly, our society depends heavily on the food provided by fruits, vegetables and grains from plants that originated in other parts of the world.

Nevertheless, those relatively few exotic pest plants cause an inordinate amount of damage to natural areas, especially the fragmented remnants of nature in our ever expanding urban communities. The control of these plants costs tax payers millions of dollars. Water hyacinths and other aquatic pest plants clog our waterways. Exotic vines like kudzu and air potato cover and kill mature forest trees. As they spread into natural areas, exotic pest plants compete with and replace native plants. In the worst cases, they crowd out endangered species and reduce the natural food supplies for native animals. After the direct destruction of natural habitats for our society’s development, exotic pest plants and animals are the greatest threat to natural environments around the world.

The conundrum is that responsible gardeners are looking for plants that are well-adapted to our local environments. We want plants that do not require soil amendments, irrigation, fertilization and pesticide applications. These are the plants, though, that have the greatest potential to spread into the natural environment. One answer may lie with the development of sterile cultivars through selection, hybridization and genetic manipulation.

Another answer is in the testing and release of predatory insects that specialize in feeding on invasive plant species. Introduced insects help control alligator weed and water hyacinth. The release of air potato beetles by the USDA in Florida in 2014 appears to be very successful. The larvae of these imported beetles eat the leaves of air potato plants, weakening them so they produce few to no aerial tubers. This limits their spread. Hopefully, continued feeding will starve the underground tubers.

As gardeners, and as tax payers who foot the bills for exotic pest plant removal, we must be responsible. We need to be aware of and avoid the invasive plants of our regions. We need to monitor our plants and remove from our gardens any that become invasive. If we do not manage our plants willingly, we may see our government increase its role in regulating our garden plants. Please keep up with the latest information. The Southeast Exotic Pest Plant Council website covers the Coastal Southeast region, detailing it state by state with regular updates to the state lists. The Council's website is found at http://se-eppc.org.